Open Access
Research
The effect of food environments on fruit and vegetable intake as modified by time spent at home: a cross-sectional study Antony Chum,1,2 Eddie Farrell,1 Tyler Vaivada,3 Anna Labetski,1 Arianne Bohnert,1 Inthuja Selvaratnam,1 Kristian Larsen,1 Theresa Pinter,4 Patricia O’Campo1
To cite: Chum A, Farrell E, Vaivada T, et al. The effect of food environments on fruit and vegetable intake as modified by time spent at home: a cross-sectional study. BMJ Open 2015;5: e006200. doi:10.1136/ bmjopen-2014-006200 ▸ Prepublication history for this paper is available online. To view these files please visit the journal online (http://dx.doi.org/10.1136/ bmjopen-2014-006200). Received 23 July 2014 Revised 2 December 2014 Accepted 9 January 2015
1
Centre for Research on Inner City Health, St. Michael’s Hospital, Toronto, Ontario, Canada 2 Department of Social and Environmental Research, London School of Hygiene and Tropical Medicine, London, UK 3 Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada 4 University of Toronto, Toronto, Ontario, Canada Correspondence to Dr Antony Chum; [email protected]
ABSTRACT Objective: There is a growing body of research that investigates how the residential neighbourhood context relates to individual diet. However, previous studies ignore participants’ time spent in the residential environment and this may be a problem because timeuse studies show that adults’ time-use pattern can significantly vary. To better understand the role of exposure duration, we designed a study to examine ‘time spent at home’ as a moderator to the residential food environment-diet association. Design: Cross-sectional observational study. Settings: City of Toronto, Ontario, Canada. Participants: 2411 adults aged 25–65. Primary outcome measure: Frequency of vegetable and fruit intake (VFI) per day. Results: To examine how time spent at home may moderate the relationship between residential food environment and VFI, the full sample was split into three equal subgroups—short, medium and long duration spent at home. We detected significant associations between density of food stores in the residential food environment and VFI for subgroups that spend medium and long durations at home (ie, spending a mean of 8.0 and 12.3 h at home, respectively—not including sleep time), but no associations exist for people who spend the lowest amount of time at home (mean=4.7 h). Also, no associations were detected in analyses using the full sample. Conclusions: Our study is the first to demonstrate that time spent at home may be an important variable to identify hidden population patterns regarding VFI. Time spent at home can impact the association between the residential food environment and individual VFI.
INTRODUCTION Low vegetable and fruit intake (VFI) has been linked to a number of chronic diseases, including type II diabetes,1 2 cardiovascular disease,3 4 and breast,5 6 oesophageal and
Strengths and limitations of this study ▪ Our study extends the body of work on the effects of residential food environments on diet by looking at the amount of time that participants spend at home. ▪ Previous studies ignore participants’ time spent at home, and this may be a problem because adults’ time-use can significantly vary. ▪ Cross-sectional observational data limits the study’s ability to discern the direction of causation. ▪ Our outcome measure, vegetable and fruit intake, is based on the Canadian Community Health Survey 2010, and participants self-reported the frequency per day of fruits and vegetable eaten rather than the number of servings consumed. The self-reported frequency measure may contribute to both under and over-reporting of food intake behaviour.
colon cancers.7 8 Individual level determinants of VFI have been well established in the literature, where income and education are positively associated with VFI;9–11 however, study results of the association between VFI and its potential environmental determinants are decidedly mixed. Research on the food environment has explored the impacts of food retailers on VFI (eg, supermarkets, fast food outlets, convenience stores). Studies have shown that living in proximity to supermarkets is associated with improved diet outcomes12–19 and poor diet outcomes.20 21 Some studies also show no association between residential proximity to food vendors and VFI.22 23 Along with the inconsistent findings described above, the research is also characterised by a lack of consideration for the individuals’ duration of exposure to their neighbourhood context. By ignoring the temporal dimension of exposure, previous studies may have unintentionally introduced
Chum A, et al. BMJ Open 2015;5:e006200. doi:10.1136/bmjopen-2014-006200
1
Open Access measurement bias because exposure duration may significantly differ between participants. There is a dearth of studies that have explored this problem using multilevel analyses of neighbourhood effects on individual health outcomes. Chum and O’Campo24 found that the use of time-weighted multilevel regressions to account for duration of exposure resulted in (1) improved strength of association, and (2) improved model fit in models for the association between neighbourhood-level factors (including road traffic, access to supermarkets and fast food restaurants) and cardiovascular disease risk compared to typical multilevel models that do not account for time spent in the residential neighbourhood. There is also evidence to suggest that time spent in the residential neighbourhood varies. According to the 2010 Canadian General Social Survey (CGSS) public use microdata,25 time spent at home differs significantly by age and income: analysis of variance shows that total minutes spent at home on a typical weekday differs significantly by age groups and income groups ( p
Research
The effect of food environments on fruit and vegetable intake as modified by time spent at home: a cross-sectional study Antony Chum,1,2 Eddie Farrell,1 Tyler Vaivada,3 Anna Labetski,1 Arianne Bohnert,1 Inthuja Selvaratnam,1 Kristian Larsen,1 Theresa Pinter,4 Patricia O’Campo1
To cite: Chum A, Farrell E, Vaivada T, et al. The effect of food environments on fruit and vegetable intake as modified by time spent at home: a cross-sectional study. BMJ Open 2015;5: e006200. doi:10.1136/ bmjopen-2014-006200 ▸ Prepublication history for this paper is available online. To view these files please visit the journal online (http://dx.doi.org/10.1136/ bmjopen-2014-006200). Received 23 July 2014 Revised 2 December 2014 Accepted 9 January 2015
1
Centre for Research on Inner City Health, St. Michael’s Hospital, Toronto, Ontario, Canada 2 Department of Social and Environmental Research, London School of Hygiene and Tropical Medicine, London, UK 3 Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada 4 University of Toronto, Toronto, Ontario, Canada Correspondence to Dr Antony Chum; [email protected]
ABSTRACT Objective: There is a growing body of research that investigates how the residential neighbourhood context relates to individual diet. However, previous studies ignore participants’ time spent in the residential environment and this may be a problem because timeuse studies show that adults’ time-use pattern can significantly vary. To better understand the role of exposure duration, we designed a study to examine ‘time spent at home’ as a moderator to the residential food environment-diet association. Design: Cross-sectional observational study. Settings: City of Toronto, Ontario, Canada. Participants: 2411 adults aged 25–65. Primary outcome measure: Frequency of vegetable and fruit intake (VFI) per day. Results: To examine how time spent at home may moderate the relationship between residential food environment and VFI, the full sample was split into three equal subgroups—short, medium and long duration spent at home. We detected significant associations between density of food stores in the residential food environment and VFI for subgroups that spend medium and long durations at home (ie, spending a mean of 8.0 and 12.3 h at home, respectively—not including sleep time), but no associations exist for people who spend the lowest amount of time at home (mean=4.7 h). Also, no associations were detected in analyses using the full sample. Conclusions: Our study is the first to demonstrate that time spent at home may be an important variable to identify hidden population patterns regarding VFI. Time spent at home can impact the association between the residential food environment and individual VFI.
INTRODUCTION Low vegetable and fruit intake (VFI) has been linked to a number of chronic diseases, including type II diabetes,1 2 cardiovascular disease,3 4 and breast,5 6 oesophageal and
Strengths and limitations of this study ▪ Our study extends the body of work on the effects of residential food environments on diet by looking at the amount of time that participants spend at home. ▪ Previous studies ignore participants’ time spent at home, and this may be a problem because adults’ time-use can significantly vary. ▪ Cross-sectional observational data limits the study’s ability to discern the direction of causation. ▪ Our outcome measure, vegetable and fruit intake, is based on the Canadian Community Health Survey 2010, and participants self-reported the frequency per day of fruits and vegetable eaten rather than the number of servings consumed. The self-reported frequency measure may contribute to both under and over-reporting of food intake behaviour.
colon cancers.7 8 Individual level determinants of VFI have been well established in the literature, where income and education are positively associated with VFI;9–11 however, study results of the association between VFI and its potential environmental determinants are decidedly mixed. Research on the food environment has explored the impacts of food retailers on VFI (eg, supermarkets, fast food outlets, convenience stores). Studies have shown that living in proximity to supermarkets is associated with improved diet outcomes12–19 and poor diet outcomes.20 21 Some studies also show no association between residential proximity to food vendors and VFI.22 23 Along with the inconsistent findings described above, the research is also characterised by a lack of consideration for the individuals’ duration of exposure to their neighbourhood context. By ignoring the temporal dimension of exposure, previous studies may have unintentionally introduced
Chum A, et al. BMJ Open 2015;5:e006200. doi:10.1136/bmjopen-2014-006200
1
Open Access measurement bias because exposure duration may significantly differ between participants. There is a dearth of studies that have explored this problem using multilevel analyses of neighbourhood effects on individual health outcomes. Chum and O’Campo24 found that the use of time-weighted multilevel regressions to account for duration of exposure resulted in (1) improved strength of association, and (2) improved model fit in models for the association between neighbourhood-level factors (including road traffic, access to supermarkets and fast food restaurants) and cardiovascular disease risk compared to typical multilevel models that do not account for time spent in the residential neighbourhood. There is also evidence to suggest that time spent in the residential neighbourhood varies. According to the 2010 Canadian General Social Survey (CGSS) public use microdata,25 time spent at home differs significantly by age and income: analysis of variance shows that total minutes spent at home on a typical weekday differs significantly by age groups and income groups ( p
